John nesbitt



N` PETERS. FHOTD-LITHOGRAPHER. WASHINGTON D C @einen tutes @strat ffice.

.'JonN susurra or Non'rnrmnn, VERMONT, .Assi'cNo-n To HiMsELF AND Levis. Two, or LOWELL, MASSACHUSETTS'.

Letters Patent No. 62,969, dated llfarch'lfl, 1867.

IMPROVEMENT Ibi STEAM-ENGINE SLIDE VALVES.

TO ALLWHOM Il MAY CONGERN:

Be itknown that I, JOHN NESBITT, of Northfield, county of Washington,and State ot Vermont, have invented new and useful Improvements inBalance Valves; and I do hereby declare that-the following is a full andexact description thereof, reference being. had to the accompanyingdrawings, and letters of reference marked thereon. A v l The nature et'my invention consists inl providing, for a steam chest, a balance valve7to be protected by a shield, for the purpose of. keeping the pressure ofthe steam oil' of the top of the valve, and allowing the same -to workeasy 'inthe' chest; also with an exhaust port through the valve., forthe purpose of letting the exhaust steam from the cylinder escapeVthrough the top of the steam chest.

I To enable others skilled inthe art tov make and use my invention,Iwill proceed to 'describe its construc- 4tion and operation. l i iFigure 1 represents a longitudinal section through theV centre ot usteam chest, valve, and shield..4

Figure Z'represents a plan ofa Valve-with shield face side upi- AVFigure 3 represents an end' elevation of a. valve with shield. l

a, represents the cylinder-seat; b the steam chest; c the steam-chestcover; d the valve; f the projections for therec'esscs to receivethemetallic packing g and the shield. I propose tc obvatc-and remedy thegreat pressure' of the steam acting upon the top surface of the valvesnew in use, whiclrpressure oftentimes, with the unclean and foul stateof the steamacting on the sca-t of the valve, produces great frictionwhen working, requiring unnecessary power to operate the same, andresulting in wear and chafing the 4werking surfaces ot both valveandcylinder-seats, thus rendering them ina short :space of timeunserviccablc. These objections I believeto Aa great extent are obviatedby my invention'. I construct the cylinder,- steam ehest,and otherappendages thereunto belonging, in the usual and ordinary way. I alsoconstruct the face or bottom .side of my valve lin the usual form ofslide valves. The top side I construct in various forms, but Ipx-efeitlie semicircular form as herein represented, withprojections,.for thereccption of the m'etallic packing g g, and anexhaust port c through its centre. i The top of the lvalve CZ is turnedand iinished to altrue surface to corre spend with the underside of theshiel'd Zt, which is also finished. I make recesses in .thc top of Atheprojections lfj' en the ends of the valve d, inl which I place .themetallic packing g g. I make holes, z' z', at the bottoih of theIrecesses through thcv projections f for the steam in the chest to passthrough and press against the' under side not the packing g g, for thepurpose of .pressing it outward against the under side of the-shield It.AThis packing g g I make in parts similar to the ordinary packing now'uscd in piston-heads. The shield L is made of the requisite length to'cover the valve d and packing g g therein, when the valve d is at itsextreme points, and is also open at cach end, but its sidcscxtendcverthe valve (Z to the face of the cylinder a, upon which it rests thejoints being made steam-tight.` The valve cZ does not entirely till thcspacebctween the face of the cylinder a and the shield h, a small spacebeing provided between thc top ofthe Vvalve d and the under side of theshield 7L, which forms, a chamber, Z Z, when thepacking g g in the endsof' the valve cZ is pressed outward by the steam 'against the under-sideof thel shield it, thus 'excluding the steam in the chest from-the topofthe valve-d, and thereby shielding the valve d from the great downwardpressure oi the steam in the chest, and allowing the -Yalve oZ to lmovefree and easy under the shield Zi. To prevent the valve Z from beinglifted from itsseat by the upward pressure of the steam, inthe cylinderports o o, upon its under side, partial provision is made by the chamberZ Z over the valve d; this chamber ZZ being lled with the exhaustingsteam, which enters through the exhaust .port 7c in the valve CZ, thusfilling the chamber Z Z with the exhaust steam, and applying itspressure upon the top of the valve LZ over its whole arca enclosedwithin the chamber ZZ. This in a measure counter-- balances the liftingpressure upony thc valve eZ ovtjthe steam 'in the cylinderports o ounder the valve cZ, but a furtherand full provision is made15o-counteract the lifting force of the steam under the valve rZ, by-thedownl ward pressure of the steam in the -chest Z ,'.upo n the'project-ion f on the ends of the valve d, which contain the packing gy, to which may-bc added any additional arca of surface upon the top ofthe 'valve d, exposed to the downward pressure of the stenmdn thcchestvb, by inserting the packing g g in the valve d, ata greater orless distance from the ends of the valve d, thus exposing tothelprcssurc of the steam in the chest b the necessary top surface oi'the valve d to counterbnlance the upward pressure oi' the steuni in thecyllnuer ports o ouuder it. The shield 7L, when plced in its'posit-ionover the vulve d, is held securely hy being screwed down to the incc ofthe cylinder a, or -by' any other convenient method. In enses where thesteam chest bis short for the slide of the valve d, the projectiousff on,the ends muy be dispensed with, and the peeking g g in the vulve placednearer its centre. In some cases it is desirable to exhaust directlythrough the steam chest. To accom plish this I pass'the exhaust pipenthrough the top of the steam chest c, and connect it to the top 'of theshield 7:, which th'en has a port, g, through it to correspond with theexhaust pipe n, und opening to. the chamber ZZ over the valve d, and tothe vexhaust port zin the vulve d. The exhaust pipe n is screwed throughthe l'top of the chest c upon a. ball-sent, p, on top of the shield h,where it is firmly held by the nut r, binding upon the top of the chestc. l

What I claim ns'my invention, and desire to secure by Letters lPatent,is- 1.` I claim the arrangement of the valve d, with reference to thepackinggg, in its ends, substantially :is

herein described. Y

2. I claim the chamber ll over the valve d, constructedin the manner undfor the purpose substantially as herein set forth. i v I 3. I claim thecombination and arrangement of the valve cl, shield L, chamber l l, undexhaust port k, for

the purpose suhstuntiallyas described.l

4. I claim the projectionsfon the ends'of the volvo d, constructed inthe manner Vund for the purpose substantially as her-ein described andset forth.

" JOHN. NESBITT.

Witnesses GEO. H. CRANE, J. C. B. T11/msn.

